Amyotrophic lateral sclerosis (ALS), commonly known as Lou Gehrig’s disease or classical motor neuron disease, is a progressive and ultimately fatal disorder that disrupts signals to all voluntary muscles. In the United States, ALS and motor neuron disease are used interchangeably. It affects both upper and lower motor neurons. Around 75 percent of individuals with classic ALS also experience weakness and wasting of bulbar muscles, which control speech, swallowing, and chewing.
Symptoms typically manifest first in the arms and hands, legs, or swallowing muscles, with muscle weakness and atrophy affecting both sides of the body disproportionately. This leads to a loss of strength and mobility in the arms, legs, and body. Other symptoms include spasticity, exaggerated reflexes, muscle cramps, fasciculations (muscle twitching), and difficulties with swallowing and speech. Speech may become slurred or nasal. When the muscles involved in breathing, such as those of the diaphragm and chest wall, fail to function properly, individuals require mechanical support for breathing. While ALS typically does not affect cognitive functions, some individuals may experience alterations in decision-making and memory.
ALS most commonly affects individuals aged 40 to 60, although it can occur in younger and older individuals as well, with men being more frequently affected than women. Most cases occur sporadically, with no increased risk for family members, although a familial form exists, often linked to mutations in the superoxide dismutase gene (SOD1). A rare juvenile-onset form is also genetic. Respiratory failure is the primary cause of death, usually occurring within 3 to 5 years from symptom onset, although some individuals may survive for 10 or more years.
Progressive bulbar palsy, or progressive bulbar atrophy, involves the bulb-shaped brain stem controlling lower motor neurons necessary for swallowing, speech, and chewing. Symptoms include weakness in pharyngeal muscles involved in swallowing, weak jaw and facial muscles, progressive speech loss, and tongue muscle atrophy. Limb weakness with both lower and upper motor neuron signs is present but less prominent. Emotional lability, with outbursts of laughing or crying, is common. Individuals may become unable to eat or speak, increasing the risk of choking and aspiration pneumonia.
Pseudobulbar palsy shares symptoms with progressive bulbar palsy, characterized by upper motor neuron degeneration leading to progressive loss of speech, chewing, and swallowing abilities. Facial muscle weakness results in a fixed facial expression, while the tongue may become immobile.